Co-crystallization of dextrose and sucrose on cereal products

ABSTRACT

Dextrose and sucrose are co-crystallized onto the surface of breakfast cereal products such as corn flakes, puffed wheat or puffed rice, by applying to the surface of said cereal product a powdered crystalline material comprising any of sucrose, dextrose or mixtures thereof, and coating the surface with a layer of a concentrated aqueous solution of dextrose and sucrose. The coated cereal product is then dried at a temperature below the browning temperature of the product. The resulting coated cereal product has a desirable frosted appearance.

This is a continuation of copending application Ser. No. 118,697, filedFeb. 5, 1980, now abandoned which in turn is a continuation ofapplication Ser. No. 888,707, filed Mar. 20, 1978, now abandoned, whichin turn was a division of application Ser. No. 756,931, filed Jan. 5,1977, now U.S. Pat. No. 4,101,680.

BACKGROUND OF THE INVENTION

This invention relates to presweetened breakfast cereal products, andmore in particular, to cereal products which have been coated withmixtures of sugars to produce a variety of presweetened cold breakfastcereal products for direct sale to the consumer. The sugars coated ontothese cereal products have, at least in part, crystallized, therebygiving a consumer-pleasing frosted effect to the product.

Presweetened cold breakfast cereal products have been sold on theconsumer market for many years. Generally, the sugar material which wascoated on the surface thereof was sucrose. However, during the pastseveral years when the cost of sucrose has risen, interest has beenshown in utilizing a substitute for sucrose; such as, corn syrup solidsor dextrose which are generally lower in cost than sucrose.Unfortunately, however, the use of these materials produces presweetenedcereals which tend to be hygroscopic, and where the sugar is notcrystalline. Rather, these coatings tend to be hard, glassy-type,transparent coatings which tend to become tacky upon storage. Recently,procedures have been developed in the art which enable these coatings tobe applied in a form which is relatively non-hygroscopic.

However, it has been found that the use of dextrose ordextrose-containing materials as the coating material on cereal productsyields products which are insufficiently sweet for the consumer market.It is thus desirable to replace only a portion of the previouslyutilized sucrose with the dextrose or dextrose-containing material.Prior to this invention, it has not been possible to produce a coatingon a breakfast cereal product wherein dextrose and sucrose areco-crystallized onto the surface of the cereal product. Through theutilization of the process of this invention it is, however, possible toform frosted crystalline coatings on these cereal products wherein atleast a portion of the dextrose and sucrose are in the crystallinestate.

SUMMARY OF THE INVENTION

An aqueous solution of dextrose and sucrose in a pre-determined ratio isformed at a solids concentration of about 30 to 45% dry substance. Thisaqueous solution is maintained at a temperature above the saturationtemperature of the sugars. A breakfast cereal product is substantiallyuniformly coated with seed crystals of dextrose, sucrose or a mixturethereof. The previously formed aqueous solution is then coated onto thesurface of the cereal product in a substantially uniform manner. Thecoated cereal product is then dried with controlled heating to reducethe moisture content of the coating. The temperature should alwaysremain below that which can cause browning of the cereal product. Thedrying is continued until a moisture content of not less than about 3%to about 4% remains in the coating. The coated cereal product is thensealed and stored. The coating gradually whitens due to the formation ofcrystals on the surface and the crystallization is generally completeafter a period of about 2 to 3 days.

It is possible to introduce the said material and sugar solution ontothe surface of the cereal product either simultaneously or in eitherorder, provided a uniform distribution of both materials is obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is useful to produce a wide variety of presweetenedbreakfast cereal products. Generally, the process may be utilized toproduce any frosted breakfast cereal product which has beenconventionally produced with a sucrose coating.

An aqueous solution of dextrose and sucrose is formed having apredetermined ratio of dextrose to sucrose. Generally, any commercialform of dextrose or sucrose may be used; e.g., the commercial granulatedsucrose, anhydrous dextrose, dextrose monohydrate, liquid dextrose andhigh dextrose corn syrup, provided these corn syrups do not containexcessive levels of impurities, which levels could retard or preventcrystallization. The particular form of dextrose is not critical, aswhen placed in aqueous solution all are identical. It is, of course,necessary that the weight of water of hydration be taken in account.

The solution is formed in any conventional manner. Generally, it is mostconvenient to utilize as high a solids concentration as possible so thatthe subsequent drying step may be carried out as quickly as possible.Generally, the optimum value is the highest which may be convenientlyhandled; i.e., agitated, pumped, sprayed, etc. Based on theseconsiderations, it has been found convenient to utilize solutions havingfrom about 75% to about 88% total solids and preferably about 85%.

In practicing the process of this invention, any desired dextrose tosucrose ratio may be utilized. The selection of the ratio which isdesired will depend upon the particular application, and the desiredsweetness level of the final product. Thus, while crystallization of thesugar solution may be done at any values of the dextrose to sucroseratio, the ultimate selection will be based upon the taste,hygroscopicity, and economic considerations dictated by the particularmarket for the final product. Experimentally, satisfactory products havebeen prepared utilizing dextrose to sucrose ratios ranging from 85:15 to25:75.

It is to be expected that the most satisfactory results may be obtainedwhen utilizing ratios in which one sugar predominates. This is due tothe fact that each of the sugars can function as an impurity retardingthe crystallization of the other. Thus, when utilizing dextrose tosucrose ratios near 50:50, the rate of crystallization may besubstantially slower than when utilizing other ratios of dextrose tosucrose; as at a 50:50 ratio each sugar can be considered to be amaximum impurity of the other.

The aqueous sugar solution should be unsaturated with respect to bothsugars; so as not to crystallize in the solution. Generally, convenientoperating temperatures will vary from about 90° C. to 100° C., but suchis not critical.

The unsweetened breakfast cereal product is first treated by coating itssurface with either a sucrose or dextrose powdered crystalline material.While certain sucrose to dextrose ratios may crystallize satisfactorilywithout seeding, and in particular those wherein sucrose is thepredominant sugar, it is preferred that the surface of the cerealproduct be coated with these seed crystals. In general, the seedmaterial may be sucrose, anhydrous dextrose or dextrose monohydrateinterchangeably. However, where dextrose makes up at least about 65% ofthe total sugar in the solution, seeding with either anhydrous dextroseor dextrose monohydrate is superior to seeding with sucrose. Where lessthan about 65% of the total sugar is dextrose, the choice of seedcrystal is immaterial.

The seeding is performed in any conventional manner which will uniformlycoat the surface, such as by dusting or tumbling the dry cereal productwith a quantity of finely comminuted seed material. The quantity of seedmaterial utilized is not critical. An excess of seed material may beutilized if the excess can be removed from the system. Generally, theamount of seed material adhering to the surface will be about 1% to 2%based on weight of the cereal product when using corn flakes as thecereal product. The sieve analyses of the seed materials used in thefollowing example are set forth in Table I. These, however, areillustrative only.

                  TABLE I                                                         ______________________________________                                        U.S. Standard                                                                              Dextrose    Anhydrous                                            Sieve        Monohydrate Dextrose   Sucrose                                   ______________________________________                                        +30          5.6         0          0                                         -30 + 50     11.7        2.0        0                                          -50 + 100   23.5        20.2       4.0                                       -100 + 200   34.2        40.3       36.3                                      -200 + 325   16.9        22.8       50.2                                      -325         8.1         14.7       9.5                                       ______________________________________                                    

The sugar solution is then applied in a thin, uniform coating onto thesurface of the cereal product. It is convenient to spray the surfacewith the solution, but the mode of application is not crucial so long asthe proper coating is obtained.

Another suitable method would be what is called the "random drip method"as described in U.S. Pat. No. 3,959,498.

It has been found that the amount of coating material applied to thesurface is preferably in the range of about 25% to about 45%, dry basis,based on weight of the cereal product. A most preferable amount is about35%. These amounts, may, of course, be varied depending on the desiredsweetness of the final product.

The moisture content of the applied sugar solution is then reduced.There are two important considerations here--drying temperature andfinal moisture content of the coating.

With regard to the temperature at which the moisture content is reduced,it is important that the temperature not be sufficiently high to producean unacceptable browning of the product which may happen in the presenceof a reducing sugar. The particular drying temperature utilized isrelated to the drying time; i.e., higher temperatures may be used whenthe times are short. Commercially feasible conditions for drying wouldbe a temperature of about 100° C. to about 120° C. for about 30 minutesor less.

The moisture content of the coated material should be such that thecrystallization is facilitated. In general, crystallization will beinhibited if the total moisture content is reduced below 3 to 4%. Thisis believed to be due to the fact that crystal growth occurs on thefaces of the seed material. The rate of crystallization is in partcontrolled by the rate of diffusion in the coating solution. Ifoverdrying occurs, the mobility of the dextrose and sucrose is reduced,and thus crystallization is impeded and a gloss tends to form. On theother hand, excess moisture is to be avoided, as any free water presentcan be absorbed by the cereal product causing it to become sodden. Theoptimum moisture content, therefore, is less than or equal to the amountrequired to hydrate the dextrose, but, in any event, not less than about3 to 4%. Preferably, it is the lowest workable amount, such as, forexample, 4-7%.

Any method of drying may be used. It is necessary that the dryingapparatus be such that it can agitate the material during the dryingoperation to prevent agglomeration. Examples of such are a verticalturbo-dryer or an agitated belt dryer. On a laboratory scale, thematerial may be air-dried under ambient conditions.

It is to be understood that the dextrose and sucrose co-crystallize andare not believed to form mixed crystals. In addition, it is not to beexpected that all of the sugars present will crystallize, but that asubstantial portion will be crystalline, this portion being sufficientto impart the desirable frosted appearance.

The process and products of this invention are more specificallyillustrated in the following non-limiting example.

EXAMPLE

1. Preparation of Sugar Solution

The ingredients described below are heated under agitation to 90° C. to100° C. so as to completely dissolve the sugars:

    ______________________________________                                                  Batch Number                                                                  1      2      3      4    5    6                                    ______________________________________                                        Anhydrous                                                                     dextrose, % 60.0.sup.(a)                                                                           20.0   74.5 56.2 65.5 23.5                               Sucrose, %  20.0.sup.(a)                                                                           57.4   10.5 28.1 18.8 61.2                               Distilled Water, %                                                                        20.0.sup.(a)                                                                           22.6   15.0 15.7 15.7 15.3                               Dextrose: Sucrose                                                                          75:25.sup.(a)                                                                         25.8:  87.6:                                                                              66.7:                                                                              77.7:                                                                              27.7:                                                   74.2   12.4 33.3 22.3 72.3                               ______________________________________                                         .sup.(a) Calculated-                                                     

Although anhydrous dextrose was used in all the above tests, there islittle doubt that hydrate dextrose and liquid dextrose would also besatisfactory for solution make-up.

The solids concentration should be as high as can be transported, tominimize the drying required later; crystallization considerations limitthe solids content to a maximum of about 96%. A value of 85% wasselected for these tests as being the maximum which could be handledwith the available equipment.

2. Preparation of Corn Flakes

Special treatment of the corn flakes was required to determine theeffect of seeding on crystallization of the sugar solutions describedabove. For these experiments, seeding was stimulated by dusting the cornflakes with powdered, crystalline sugar (sucrose, anhydrous or hydratedextrose). This dusting was accomplished by agitating a mixture of plaincorn flakes and powdered sugar until the cereal surface was uniformlydusted, then sieving off excess sugar. The estimated seed concentrationwas 1.5% of the plain cereal weight. For each experiment plain cornflakes were used as an unseeded control.

The type of seed used in each of the tests is summarized as follows(U=unseeded; S=sucrose; D=dextrose; DH=hydrate dextrose):

    ______________________________________                                        Batch              Seed                                                       No.                Type                                                       ______________________________________                                        1                  U, S                                                       2                  U, S                                                       3                  U, S                                                       4                  U, S                                                       5                  U, S, D, DH                                                6                  U, S, D                                                    ______________________________________                                    

3. Spray Application of Sugar Solution Onto Corn Flakes

For all tests, the sugar solutions were sprayed onto corn flakes bymeans of pneumatic atomizing nozzle (Spraying Systems Company: fluidnozzle #2850, air nozzle #64), where nitrogen was used as the atomizinggas. Sugar solution was delivered to the nozzle by pressurizing thesolution-containing vessel to about 20 psig, thus forcing the solutionout of the vessel through a dip tube immersed in the solution. Theatomizing nitrogen pressure varied from 25-40 psig. The estimatedapplied sugar dosage was about 35% based on plain cereal weight. Anymethod by which a thin coating of sugar solution could be applied to thecereal surface would be satisfactory. In the above describedconfiguration, vessel and atomization pressures were selected based onthe characteristics of the available nozzle and convenience. Also, thereis nothing significant in the use of nitrogen as the atomizing gas; airwould be as good.

To achieve a uniform distribution of sugar solution on the total cerealsurface area, a commercial process would require some means of agitatingthe cereal during application. For these experiments, however, we werenot concerned about obtaining a total coating, and no cereal agitationwas used.

4. Drying the Coated Cereal Flakes

Following the application of the sugar solution, the corn flakes weredried, then treated in a variety of ways to observe the effect ofcrystallization. Up to this point the procedures, as describedpreviously, varied little from test to test. Because the dryingoperation appears to be critical to the degree of crystallizationattained, this portion of the tests will be described on a test-to-testbasis.

Batch 1: Dextrose:Sucrose 75:25 Unseeded, sucrose seeded

The unseeded and sucrose-seeded samples were split for drying at ambientconditions and at 71° C. for 45 minutes. All samples were left exposedto the atmosphere, where after a period of 2-3 days, lightcrystallization was observed on those samples which had been seeded.Subsequent desiccation of all samples produced no visable change.

Batch 2: Dextrose:Sucrose 25:75 Unseeded, sucrose seeded

The unseeded and sucrose-seeded samples were split for drying at ambientconditions and at 60° C. and 150° C. for 45 minutes. After the evendrying, all samples were left exposed to the atmosphere, where after 2to 3 days, light crystallization was observed on all samples, seeded andunseeded, except those dried at 150° C. In addition to showing nocrystallization, the flakes dried at 150° C. turned dark brown.

Batch 3: Dextrose:Sucrose 85:15 Unseeded, sucrose seeded

The unseeded and sucrose-seeded samples were split for drying at ambientconditions and at 60° C. and 150° C. for 1 hour. All samples were leftexposed to the atmosphere overnight. The next day, portions of eachsample were: (1) desiccated; (2) bottled; or (3) placed in an oven at60° C. for one hour. From the oven, separate samples were: (1)desiccated, (2) bottled, or (3) exposed to the atmosphere.

All corn flake samples which were initially dried at 150° C. turned darkbrown, with no crystallization observed. All samples which ended theirtreatment with desiccation (except those dried at 150° C.) showed lightcrystallization. All samples (except those dried at 150° C.) which endedtheir treatment by exposure to the atmosphere showed moderate to heavycrystallization. Those samples which were bottled immediately followingthe second 60° C. treatment showed no crystallization and were verysticky.

When the immediately bottled samples failed to crystallize after abouttwo weeks, they were opened and portions were removed and exposed to theatmosphere; the remaining portion of the samples were resealed. Thoseflakes exposed to the atmosphere began to crystallize after about 4 to 6days; those remaining in the bottle did not crystallize.

Batch 4: Dextrose:Sucrose 65:35 Unseeded, sucrose seeded

The unseeded and sucrose-seeded samples were split for drying at ambientconditions and at 60° C. for one and two hours. After the drying period,all samples, except the seeded air-dried sample, were placed indesiccation. The excepted sample was left exposed to the air. Afterthree days, all samples were bottled. On inspection 18 days later, theonly sample which had crystallized was the sample which had not beendesiccated. At this point, portions from all samples were exposed to theatmosphere, with the remaining portion being immediately resealed. Afteran additional eight days, all samples left sealed showed no change.Those opened to the air all showed light to moderate crystallization,including those which had not been seeded.

Batch 5: Dextrose:Sucrose 75:25 Unseeded, sucrose, anhydrous and hydratedextrose seeded

The corn flakes seeded with hydrate dextrose were dried at 45° C., theremaining at 60° C., for times from 20 to 240 minutes. After drying eachsample was immediately sealed. The solids content of the coatingsolution was measured at each time of sampling. After five days, resultsindicated crystallization only on those samples seeded with anhydrous orhydrate dextrose. In addition, little or no crystallization was observedon those samples which were dried for longer than two hours, whichcorresponds to a coating solution content of 94 to 95%.

Batch 6: Dextrose:Sucrose 25:75 Unseeded, sucrose and anhydrous dextroseseeded

The three sets of coated corn flake samples, differing in seed type,were dried at 60° C. for times varying from 20 minutes to 18 hours.After drying each sample was immediately sealed. After four days,results indicated no crystallization on the unseeded samples; thesucrose and dextrose-seeded samples showed roughly equivalent degrees ofcrystallization.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodification, and this application is intended to cover any variations,use or adaptions of the invention following, in general, the principlesof the invention and including such departures from the presentdisclosure as come within the known or customary practice in the art towhich the invention pertains and as may be applied to the essentialfeatures hereinbefore set forth, and as fall within the scope of theinvention.

What is claimed is:
 1. A presweetened coated breakfast cereal producthaving a frosted appearance wherein the coating consists essentially ofa thin, uniform layer of co-crystallized dextrose and sucrose.
 2. Aproduct in accordance with claim 1 wherein the quantity of coatingmaterial is in the range of about 25% to about 45%, dry basis, based onweight of the cereal material.
 3. A product in accordance with claim 1,wherein said cereal material is corn flakes.